<s>
is	O
a	O
command	B-Application
on	O
Unix-like	B-Operating_System
operating	I-Operating_System
systems	I-Operating_System
that	O
can	O
be	O
used	O
to	O
securely	O
delete	O
files	O
and	O
devices	O
so	O
that	O
it	O
is	O
extremely	O
difficult	O
to	O
recover	O
them	O
,	O
even	O
with	O
specialized	O
hardware	O
and	O
technology	O
;	O
assuming	O
it	O
's	O
even	O
possible	O
to	O
recover	O
the	O
file	O
at	O
all	O
.	O
</s>
<s>
It	O
is	O
a	O
part	O
of	O
GNU	B-Application
Core	I-Application
Utilities	I-Application
.	O
</s>
<s>
For	O
efficiency	O
,	O
the	O
process	O
of	O
erasing	O
a	O
file	O
from	O
storage	O
using	O
the	O
command	B-Application
usually	O
only	O
erases	O
the	O
file	O
's	O
file-system	O
entry	O
while	O
keeping	O
the	O
content	O
of	O
the	O
file	O
intact	O
.	O
</s>
<s>
By	O
default	O
,	O
the	O
command	B-Application
overwrites	O
the	O
file	O
three	O
times	O
with	O
multiple	O
patterns	O
,	O
but	O
the	O
number	O
is	O
user	O
configurable	O
.	O
</s>
<s>
By	O
default	O
,	O
shred	B-Application
also	O
shreds	B-Application
file	O
slack	O
(	O
unused	O
space	O
in	O
file	O
allocations	O
)	O
.	O
</s>
<s>
Shred	B-Application
has	O
an	O
option	O
to	O
overwrite	O
only	O
the	O
file	O
itself	O
,	O
as	O
well	O
as	O
an	O
option	O
to	O
delete	O
the	O
file	O
after	O
it	O
has	O
completed	O
operation	O
.	O
</s>
<s>
Copies	O
can	O
manifest	O
themselves	O
in	O
a	O
variety	O
of	O
ways	O
,	O
such	O
as	O
through	O
manual	O
and	O
automatic	O
backups	O
,	O
file	O
system	O
snapshots	O
,	O
copy-on-write	O
filesystems	O
,	O
wear	B-Application
leveling	I-Application
on	O
flash	O
drives	O
,	O
caching	O
such	O
as	O
NFS	B-Protocol
caching	O
,	O
and	O
journaling	B-Application
.	O
</s>
<s>
If	O
available	O
,	O
the	O
SATA	O
secure	O
erase	O
command	B-Application
,	O
issued	O
through	O
hdparm	B-Application
or	O
a	O
similar	O
utility	O
,	O
may	O
be	O
helpful	O
in	O
this	O
situation	O
.	O
</s>
<s>
Physical	O
destruction	O
may	O
be	O
necessary	O
to	O
securely	O
erase	O
devices	O
such	O
as	O
memory	B-Device
cards	I-Device
and	O
unusable	O
hard	O
disks	O
.	O
</s>
<s>
The	O
Scrub	O
command	B-Application
overwrite	O
sequence	O
of	O
data	O
being	O
compliant	O
with	O
a	O
Dec	O
.	O
2005	O
draft	O
of	O
National	O
Nuclear	O
Security	O
Administration	O
Policy	O
Letter	O
NAP-14.x	O
.	O
</s>
